Comparing the photocatalytic performance of GO/ZnO and g-C3N4/ZnO composites prepared using metallurgical waste as a source of zinc

Abstract

Acid leachate from steel sludge was used as a source of zinc oxide (ZnO-L) for the preparation of photocatalytically active composites based on GO/ZnO-L and g-C3N4/ZnO-L (further denoted as gCN/ZnO-L). The prepared composites were characterized using UV–Vis spectrophotometry, SBET, XRD, FTIR and DRS. The photocatalytic efficiency was tested using the photodegradation of azo dye Acid Orange 7. The obtained results were confronted with model composites prepared from pure components. For GO/ZnO-L and gCN/ZnO-L samples, the degradation efficiency was found to be 60.2 % and 51.5 %, respectively. While in the case of gCN/ZnO-L composites, it was purely photochemical degradation, in the case of GO/ZnO-L composites adsorption was significantly co-applied. For both composites containing ZnO-L, a higher photo-degradation activity against azo dye was found compared to the model composites. The reason is the modification of the electronic structure and the emergence of new quantum levels between the valence band and the conduction band of ZnO and gCN due to the presence of other metal oxides in ZnO-L, which leads to a more efficient separation of photo-generated charge carriers.